But many popes in the past have dug out the bones of their predecessors out of contempt for them and ground them to dust and scattered them in rives.

No this simply not the case. Some graves of popes are now lost because they were destroyed in the many wars in Rome, but I cannot think of a single pope who destroyed another pope's grave. Even arguably the most unworthy of the popes, Alexander vi was buried and his gave can still be found today:

This pope had a string of lovers, attended orgies, established a brothel in the Vatican, appointed his children to be dukes and cardinals, and murdered at least 2 people... His uncle was also a pope who was little better and his buried next to him.

There is a strict distinction between the person and the office he holds... Alexander vi was so hated what the papal chamberlain, upon his death, had to place the body in a safe place and he had to threaten the Roman clergy with excommunication to get them to say funeral prayers for him. Still, he was buried in the end, and most attempted to forget him ... still, the papacy survived him, but only just...

Something could have been done with Charlemagne for

a)conversion by sword of pagans

well if you read the accounts of the Saxon conquest, Charlemagne had those Saxons killed who REFUSED to ACCEPT HIS RULE. The war was in two phases, and after the first he sent missionaries. However, when later churches were attacked and destroyed, he returned and this time he forced a conversion, as a way to quell rebellion. At the time this course of action was not widely criticised, but was later. Sadly, this is a failing of the Church, something they could have done better.

This charge however is levelled falsely against him. He had a total of 4 wives, but not at the same time, one after the after the other.

As a young man he had a mistress called Himiltrude whith who he a a Son, Pippin the Hunchback, who later rebelled against him as was banished to a monastery.

Charlemagne’s first wife was the daughter of Desiderius, a king of the Lombards. He married her by his mother’s persuasion for political reasons. Marriage did not last long, because Charlemagne dispelled her after one year, so he could marry Hildegard, who was of Swabian origin.

The young queen has accompanied Charlemagne in almost all campaigns. They’ve had four sons and five daughters. She died very young, when she was only 26 years old. She was buried in the Metz Cathedral. Numerous legends of her character appeared soon after. In them, she is referred by the name Blanchefleur.

Soon after her death he married Fastrada, a daughter of Austrasian count Radolf. She became Charlemagne’s wife after Hildegard’s death, and she died in 794. According to Einhard, she was beautiful, ambitious and cruel, and in the public opinions she had a negative influence on Charlemagne.

After her death, he married Liutgard with whom he had no children, and who was remembered as ailing, but good and devout queen. She died in 800, and was buried in Tours.

After her death he had another four mistresses and five more children.

So sure, he was married several times one after the other, and he also had affairs. That does not amount to polygamy.

Well until 1960s,the church firmly is said to have stood by its doctrine of supporting slavery,it altered the same only after there was strong public opinion against it.

This is also not accurate historically. Biblical texts were all written when slavery was an accepted fact of life. Paul severely criticised the practive of sexual slaves in Rome, but stopped short of condemning slavery outright.

If you look a later theologians you get a mixed picture: Augustine was against slavery on the whole, whereas Thomas Aquinas only went as far as laying down rules for the treatment of slaves. If you go through the list of popes from the early middle ages to modern times in wiki, you find a handy comment for each about his views on slavery. You find a mixed picture: some speaking out against it, some for it with qualifications, some ambivalent.

What happened in the Second Vatican Council is something that should happened hundred of years before: A detailed discussion and a formal expression of a view. What the council actually said can in fact be found in many texts written long before, only there are others who argued against it.

Sadly very often the Church is very slow to respond to social issues, but it getting better.

When you believe you are only saving souls by forced conversion, that itself is an acceptance of the concept in a religion.Even if the elders that converted fail to believe in a religion due to them being forced, the following generations who will be subject to hapless brainwashing would believe indeed believe in the senseless dogma installed by the religion.

Prime Minister Narendra Modi waived loans to the tune of hundreds of thousands of rupees for corporate firms.Yet he is not prepared to give even a few thousand crores to debt ridden remnant Andhra Pradesh(debts due to unjust division in 2014) for constructing the national project of Polavaram.